1. Field of the Invention
The invention relates to a method of controlling the water permeability of a coating, and more particularly it relates to a method of controlling the water permeability of an organosilicone coating applied to a substrate.
2. The Prior Art
The use of moisture-permeation barriers is well known in the art, and indeed such barriers are in every day use. Typically, they are employed for corrosion protection, passivation of electronic circuits, etc. Thus, for instance, in dielectrics utilized in hostile environmental applications, the electrical conductivity of such dielectrics is substantially affected by the presence of humidity through its mobilization of otherwise immobile ions and it is often desirable and/or necessary to provide a barrier which will reduce moisture permeation, enhancing the performance and the lifetime of the device. There are many known water-permeation barriers, such as polymers, and they have received extensive use. However, they do also suffer from some inadequacies, such as poor adhesion, shrinkage, water sensitivity, and too high water permeation for certain uses. Other methods for barring entry of moisture include hermetically sealing or fusing metal-metal, metal-glass or metal-ceramic, etc.; however, not only are such methods costly and extremely time-consuming, they increase the size of the device, thus compromising commercial advantages of a product.
It is an object of the present invention to provide a method of controlling the water permeability to a substrate such that, in many instances, a lower permeability of a topcoat film covering a substrate will limit the amount of water reaching the substrate.